Modern memory types include volatile memory and non-volatile memory. Both types of memory are used to store and retrieve information. Non-volatile memory is capable of storing information even after the memory is disconnected from a power supply. Thus, when the non-volatile memory is subsequently connected to a power supply and powered up, information previously stored in the non-volatile memory may be accessed. In contrast, volatile memory is typically incapable of storing information when the memory is disconnected from a power supply for a given period of time.
In some cases, there may be a desire to provide non-volatile and volatile memory storage capability for a single device. For example, after manufacturing a volatile memory device, the device may be tested to determine if there are any defects in the device. The device may also include repair circuits which may be used to repair defects in the device. In order to record test and repair information without losing the information when the device is disconnected from a power supply, non-volatile storage within the device may be used.
In some cases, providing non-volatile memory storage capability to a device may undesirably increase the cost of the device. For example, some non-volatile storage techniques may use additional manufacturing steps or materials which increase the cost of the device. Other non-volatile storage techniques, such as using laser-blown fuses to store information, may be undesirably restricted to storing information only at certain times in the manufacturing process, for example, before the device has been packaged.
Accordingly, what is needed is an improved method and apparatus for providing non-volatile memory storage.